Research On CFD Simulation Of Overtaking By Switching Lines

With the rapid development of mechanical manufacturing technology and increase of the numbers of highways, the time of high-speed running has been greatly increased and the driving conditions become more complex. When the cars are overtaking at a high speed, the flow fields around the car body will change constantly and produce a strong aerodynamic interference. It will result the constant changing of the six-pitch forces and cause shifts of vehicles, which seriously affect the stability and security of the vehicles. The annual collisions of automotive have a large proportion of overtaking with a high speed in china. Therefore, the research of aerodynamic characteristics during the high speed overtaking is very important and meaningful.Many famous universities and research institutes have finished the calculation and simulation of overtaking by CFD (Computational Fluid Dynamics) analysis process, but so far the most of the CFD calculation methods are based on discontinuous mesh method. The overset mesh and discontinuous mesh will be used respectively on the numerical simulation of the external flow field of overtaking in line based on the Ahmed model. In this process, the applicability and accuracy of overset mesh method in simulating the automotive external flow field are proved by comparing the variation of the aerodynamic coefficient and the distribution of body surface pressure. The principle and the problems of the calculation of the overset mesh method are pointed out, and the solving ways are analyzing too.Thus, the overset mesh method is used to finish the numerical simulation of the external flow field of overtaking by switching lines for the first time. The variation law of the aerodynamic interference is researched by the analysis of the variation of the aerodynamic coefficient and the effects to the safety are analyzed.These calculations show the potential of the overset mesh method to solve the problems such as overtaking by switching lines and provide a way to solve such problems of the actual vehicles.